In an attempt to reduce emissions, efforts have been made to utilize substantially carbon-free hydrogen as a combustion fuel instead of hydrocarbons. When hydrogen (H2) is used as the fuel, there is not a substantial amount of HC, CO, or CO2 emissions, because the fuel does not include carbon that can be turned into HC, CO, or CO2. Therefore, hydrogen fuel is currently viewed as a potentially good fuel choice for environmentally clean internal combustion engines.
Hydrogen can also be used as an energy source by a variety of other devices. For example, a fuel cell can convert hydrogen into electrical energy using an environmentally clean reaction.
Although hydrogen fuel systems may be an environmentally desired option over hydrocarbon systems, hydrogen systems may suffer from hydrogen leakage. Specifically, hydrogen is a small molecule that is capable of passing through material pores, very small system openings, and/or seal asperities. When designing a hydrogen fuel delivery system (e.g., for an internal combustion engine, fuel cell, or other device), every connection or penetration of the boundary of the fuel delivery system may be a possible hydrogen release path. In particular, if hydrogen is stored as high pressure gas, high pressure connections (e.g., the first or second high pressure reducing regulators, fuel pressure sensing or quantity gauging, and/or any electrical or manual shutoff devices) may be susceptible to hydrogen leakage.
In the past, attempts have been made to mitigate hydrocarbon fuel leakage by completely enveloping portions of a fuel delivery system in a capsule, or by creating secondary seals and/or containment chambers around connections and boundaries of the fuel delivery system. For example, U.S. Pat. No. 6,571,978 discloses one such approach for reducing the amount of hydrocarbons which are given off to the ambient atmosphere.
Further, as another example, United States Patent Publication Number 2004/0154314 discloses a capsule that is designed to trap hydrogen gas that escapes a liquid hydrogen cryotank fuel delivery system. As with the hydrocarbon fuel delivery system described above, this approach merely attempts to mitigate the harmful affects of leakage by containing the leakage so that it can be treated before being released to the atmosphere.
The inventors herein have recognized the need to reduce or limit fuel leakage and potential drawbacks with current approaches for a hydrogen or gas-based system. As described above, each coupling in a hydrogen system may be a potential hydrogen leakage point. Further, some current systems use intermediate containment areas in an attempt to control gaseous fuel leakage. However, dangerous gases may accumulate in the intermediate containment areas and a venting system may be needed to handle the leaked gases. The intermediate containment capsule, the venting system, and/or other aspects of such a system may increase cost and/or limit spatial design freedom. Furthermore, any fuel leakage may reduce overall fuel efficiency.
As an example, at least some of the issues associated with gaseous fuel leakage may be addressed by a fuel delivery system that includes limited connections at which fuel may leak from the system. As an example, a storage tank may be used to hold a gaseous fuel, and the fuel may be converted by a powerplant to energy that is useable to power a vehicle. The fuel stored in the tank may be delivered to the powerplant by an uninterrupted passage fluidically coupling the storage tank to the powerplant. In some embodiments, a pressure regulation system may be located interior the storage tank. The pressure regulation system may decrease or increase the pressure of the gaseous fuel so that the gaseous fuel is suitable for delivery to the powerplant.
In this manner, the number of connections intermediate the fuel tank and the powerplant may be limited, thus minimizing opportunities for gaseous fuel to leak from the system. Because the pressure regulation system is physically located within the storage tank, any leakage that occurs in the pressure regulation system may return to the storage tank. By using an integrated fuel delivery system, gas leakages may be reduced and fuel efficiency improved.